1. Field of the Invention
The present invention relates to an image signal recording device by which an image signal generated in accordance with the HDTV (High Definition TV) mode and the like is recorded on a magnetic disk in accordance with a standard television mode and the like.
2. Description of the Related Art
Conventionally, a still video device is constructed in such a manner that an image signal generated in accordance with a standard television mode (the NTSC mode, for example) is recorded on a track of a magnetic disk in accordance with a still video format. The bandwidth of the image signal is limited, due to the construction of the disk device, and thus cannot be freely expanded. Accordingly, in a conventional still video device, when an image signal having a high quality, or broad bandwidth, is inputted to the still video device, the image resolution is limited, and thus, the quality of the image is lowered.
In Japanese Unexamined Patent Publication No. 5-30461, a still video device by which a high definition image recorded in the HDTV mode, for example, is recorded on a magnetic disk, is disclosed. In this still video device, an image signal corresponding to one image is divided into a plurality of parts, and is subsampled. Then, this subsampled image signal is time-expanded, and is recorded on a track of the magnetic disk. Namely, when an image signal corresponding to one image is divided into two parts, the image signal is recorded on four tracks in a frame mode.
The number of effective scanning lines provided in one image recorded in accordance with a high vision mode, which is one variation of the HDTV mode, is 1035. Therefore, when one image is divided and recorded on four tracks, the number of effective scanning lines recorded on one track is approximately 259. In the still video device, however, the number of effective scanning lines provided on one track of a magnetic disk is 241.5 in the NTSC mode, and therefore, all the image signal of the HDTV mode cannot be recorded on the magnetic disk.